diff --git a/bool_test.go b/bool_test.go
index a85e7873..bf866cd4 100644
--- a/bool_test.go
+++ b/bool_test.go
@@ -4,8 +4,8 @@
 package pflag
 
 import (
-	"bytes"
 	"strconv"
+	"strings"
 	"testing"
 )
 
@@ -154,7 +154,7 @@ func TestImplicitFalse(t *testing.T) {
 func TestInvalidValue(t *testing.T) {
 	var tristate triStateValue
 	f := setUpFlagSet(&tristate)
-	var buf bytes.Buffer
+	var buf strings.Builder
 	f.SetOutput(&buf)
 	err := f.Parse([]string{"--tristate=invalid"})
 	if err == nil {
diff --git a/bytes.go b/bytes.go
index 1a216815..bfdee704 100644
--- a/bytes.go
+++ b/bytes.go
@@ -49,7 +49,7 @@ func bytesHexConv(sval string) (interface{}, error) {
 		return bin, nil
 	}
 
-	return nil, fmt.Errorf("invalid string being converted to Bytes: %s %s", sval, err)
+	return nil, fmt.Errorf("invalid string being converted to Bytes: %s %w", sval, err)
 }
 
 // GetBytesHex return the []byte value of a flag with the given name
@@ -178,7 +178,7 @@ func bytesBase64ValueConv(sval string) (interface{}, error) {
 		return bin, nil
 	}
 
-	return nil, fmt.Errorf("invalid string being converted to Bytes: %s %s", sval, err)
+	return nil, fmt.Errorf("invalid string being converted to Bytes: %s %w", sval, err)
 }
 
 // GetBytesBase64 return the []byte value of a flag with the given name
diff --git a/count.go b/count.go
index 328bbbcc..3601e1f9 100644
--- a/count.go
+++ b/count.go
@@ -16,7 +16,7 @@ func newCountValue(val int, p *int) *countValue {
 func (i *countValue) Set(s string) error {
 	// "+1" means that no specific value was passed, so increment
 	if s == "+1" {
-		*i = countValue(*i + 1)
+		*i++
 		return nil
 	}
 	v, err := strconv.ParseInt(s, 0, 0)
diff --git a/flag.go b/flag.go
index 2a568339..56716359 100644
--- a/flag.go
+++ b/flag.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"errors"
 	goflag "flag"
 	"fmt"
@@ -430,7 +429,7 @@ func (f *FlagSet) Set(name, value string) error {
 		} else {
 			flagName = fmt.Sprintf("--%s", flag.Name)
 		}
-		return fmt.Errorf("invalid argument %q for %q flag: %v", value, flagName, err)
+		return fmt.Errorf("invalid argument %q for %q flag: %w", value, flagName, err)
 	}
 
 	if !flag.Changed {
@@ -607,7 +606,7 @@ func wrapN(i, slop int, s string) (string, string) {
 // caller). Pass `w` == 0 to do no wrapping
 func wrap(i, w int, s string) string {
 	if w == 0 {
-		return strings.Replace(s, "\n", "\n"+strings.Repeat(" ", i), -1)
+		return strings.ReplaceAll(s, "\n", "\n"+strings.Repeat(" ", i))
 	}
 
 	// space between indent i and end of line width w into which
@@ -625,7 +624,7 @@ func wrap(i, w int, s string) string {
 	}
 	// If still not enough space then don't even try to wrap.
 	if wrap < 24 {
-		return strings.Replace(s, "\n", r, -1)
+		return strings.ReplaceAll(s, "\n", r)
 	}
 
 	// Try to avoid short orphan words on the final line, by
@@ -637,35 +636,33 @@ func wrap(i, w int, s string) string {
 	// Handle first line, which is indented by the caller (or the
 	// special case above)
 	l, s = wrapN(wrap, slop, s)
-	r = r + strings.Replace(l, "\n", "\n"+strings.Repeat(" ", i), -1)
+	r = r + strings.ReplaceAll(l, "\n", "\n"+strings.Repeat(" ", i))
 
 	// Now wrap the rest
 	for s != "" {
 		var t string
 
 		t, s = wrapN(wrap, slop, s)
-		r = r + "\n" + strings.Repeat(" ", i) + strings.Replace(t, "\n", "\n"+strings.Repeat(" ", i), -1)
+		r = r + "\n" + strings.Repeat(" ", i) + strings.ReplaceAll(t, "\n", "\n"+strings.Repeat(" ", i))
 	}
 
 	return r
-
 }
 
 // FlagUsagesWrapped returns a string containing the usage information
 // for all flags in the FlagSet. Wrapped to `cols` columns (0 for no
 // wrapping)
 func (f *FlagSet) FlagUsagesWrapped(cols int) string {
-	buf := new(bytes.Buffer)
-
-	lines := make([]string, 0, len(f.formal))
-
-	maxlen := 0
+	var (
+		max, maxlen int
+		lines       = make([]string, 0, len(f.formal))
+	)
 	f.VisitAll(func(flag *Flag) {
 		if flag.Hidden {
 			return
 		}
 
-		line := ""
+		var line string
 		if flag.Shorthand != "" && flag.ShorthandDeprecated == "" {
 			line = fmt.Sprintf("  -%s", flag.Shorthand)
 			if !flag.ShorthandOnly {
@@ -716,8 +713,11 @@ func (f *FlagSet) FlagUsagesWrapped(cols int) string {
 		}
 
 		lines = append(lines, line)
+		max += len(line)
 	})
 
+	buf := new(strings.Builder)
+	buf.Grow(max)
 	for _, line := range lines {
 		sidx := strings.Index(line, "\x00")
 		spacing := strings.Repeat(" ", maxlen-sidx)
@@ -1149,10 +1149,6 @@ func (f *FlagSet) parseAll(arguments []string, fn parseFunc) error {
 	}
 	f.parsed = true
 
-	if len(arguments) < 0 {
-		return nil
-	}
-
 	f.args = make([]string, 0, len(arguments))
 
 	err := f.parseArgs(arguments, fn)
diff --git a/flag_test.go b/flag_test.go
index 9f7dd152..fa702f47 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -673,7 +672,7 @@ func TestChangedHelper(t *testing.T) {
 func replaceSeparators(name string, from []string, to string) string {
 	result := name
 	for _, sep := range from {
-		result = strings.Replace(result, sep, to, -1)
+		result = strings.ReplaceAll(result, sep, to)
 	}
 	// Type convert to indicate normalization has been done.
 	return result
@@ -899,7 +898,7 @@ func TestUserDefined(t *testing.T) {
 
 func TestSetOutput(t *testing.T) {
 	var flags FlagSet
-	var buf bytes.Buffer
+	var buf strings.Builder
 	flags.SetOutput(&buf)
 	flags.Init("test", ContinueOnError)
 	flags.Parse([]string{"--unknown"})
@@ -910,7 +909,7 @@ func TestSetOutput(t *testing.T) {
 
 func TestOutput(t *testing.T) {
 	var flags FlagSet
-	var buf bytes.Buffer
+	var buf strings.Builder
 	expect := "an example string"
 	flags.SetOutput(&buf)
 	fmt.Fprint(flags.Output(), expect)
@@ -927,8 +926,8 @@ func TestOutputExitOnError(t *testing.T) {
 		t.Fatal("this error should not be triggered")
 		return
 	}
-	mockStdout := bytes.NewBufferString("")
-	mockStderr := bytes.NewBufferString("")
+	mockStdout := new(strings.Builder)
+	mockStderr := new(strings.Builder)
 	cmd := exec.Command(os.Args[0], "-test.run="+t.Name())
 	cmd.Env = append(os.Environ(), "PFLAG_CRASH_TEST=1")
 	cmd.Stdout = mockStdout
@@ -1161,7 +1160,7 @@ func getDeprecatedFlagSet() *FlagSet {
 func TestDeprecatedFlagInDocs(t *testing.T) {
 	f := getDeprecatedFlagSet()
 
-	out := new(bytes.Buffer)
+	out := new(strings.Builder)
 	f.SetOutput(out)
 	f.PrintDefaults()
 
@@ -1178,7 +1177,7 @@ func TestUnHiddenDeprecatedFlagInDocs(t *testing.T) {
 	}
 	flg.Hidden = false
 
-	out := new(bytes.Buffer)
+	out := new(strings.Builder)
 	f.SetOutput(out)
 	f.PrintDefaults()
 
@@ -1197,7 +1196,7 @@ func TestDeprecatedFlagShorthandInDocs(t *testing.T) {
 	f.BoolP(name, "n", true, "always true")
 	f.MarkShorthandDeprecated("noshorthandflag", fmt.Sprintf("use --%s instead", name))
 
-	out := new(bytes.Buffer)
+	out := new(strings.Builder)
 	f.SetOutput(out)
 	f.PrintDefaults()
 
@@ -1216,7 +1215,7 @@ func parseReturnStderr(t *testing.T, f *FlagSet, args []string) (string, error)
 	outC := make(chan string)
 	// copy the output in a separate goroutine so printing can't block indefinitely
 	go func() {
-		var buf bytes.Buffer
+		var buf strings.Builder
 		io.Copy(&buf, r)
 		outC <- buf.String()
 	}()
@@ -1300,7 +1299,7 @@ func TestHiddenFlagInUsage(t *testing.T) {
 	f.Bool("secretFlag", true, "shhh")
 	f.MarkHidden("secretFlag")
 
-	out := new(bytes.Buffer)
+	out := new(strings.Builder)
 	f.SetOutput(out)
 	f.PrintDefaults()
 
@@ -1365,7 +1364,7 @@ func (cv *customValue) Type() string { return "custom" }
 
 func TestPrintDefaults(t *testing.T) {
 	fs := NewFlagSet("print defaults test", ContinueOnError)
-	var buf bytes.Buffer
+	var buf strings.Builder
 	fs.SetOutput(&buf)
 	fs.Bool("A", false, "for bootstrapping, allow 'any' type")
 	fs.Bool("Alongflagname", false, "disable bounds checking")
@@ -1401,8 +1400,6 @@ func TestPrintDefaults(t *testing.T) {
 	fs.PrintDefaults()
 	got := buf.String()
 	if got != defaultOutput {
-		fmt.Println("\n" + got)
-		fmt.Println("\n" + defaultOutput)
 		t.Errorf("got %q want %q\n", got, defaultOutput)
 	}
 }
@@ -1449,7 +1446,7 @@ func TestVisitFlagOrder(t *testing.T) {
 
 func TestUnquoteUsage(t *testing.T) {
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	var fs = NewFlagSet(t.Name(), ContinueOnError)
 	fs.SetOutput(&buf)
 	want := "Usage of TestUnquoteUsage:\n"
diff --git a/ip.go b/ip.go
index 3aebd97c..b0bb239c 100644
--- a/ip.go
+++ b/ip.go
@@ -19,6 +19,9 @@ func newIPValue(val net.IP, p *net.IP) *ipValue {
 
 func (i *ipValue) String() string { return net.IP(*i).String() }
 func (i *ipValue) Set(s string) error {
+	if s == "" {
+		return nil
+	}
 	ip := net.ParseIP(strings.TrimSpace(s))
 	if ip == nil {
 		return fmt.Errorf("failed to parse IP: %q", s)
@@ -32,8 +35,7 @@ func (i *ipValue) Type() string {
 }
 
 func ipConv(sval string) (interface{}, error) {
-	ip := net.ParseIP(sval)
-	if ip != nil {
+	if ip := net.ParseIP(sval); ip != nil {
 		return ip, nil
 	}
 	return nil, fmt.Errorf("invalid string being converted to IP address: %s", sval)
diff --git a/ip_slice.go b/ip_slice.go
index ffd8e1d3..c90dafa4 100644
--- a/ip_slice.go
+++ b/ip_slice.go
@@ -75,8 +75,8 @@ func (s *ipSliceValue) String() string {
 	return "[" + out + "]"
 }
 
-func (s *ipSliceValue) fromString(val string) (net.IP, error) {
-	return net.ParseIP(strings.TrimSpace(val)), nil
+func (s *ipSliceValue) fromString(val string) net.IP {
+	return net.ParseIP(strings.TrimSpace(val))
 }
 
 func (s *ipSliceValue) toString(val net.IP) string {
@@ -84,10 +84,7 @@ func (s *ipSliceValue) toString(val net.IP) string {
 }
 
 func (s *ipSliceValue) Append(val string) error {
-	i, err := s.fromString(val)
-	if err != nil {
-		return err
-	}
+	i := s.fromString(val)
 	*s.value = append(*s.value, i)
 	return nil
 }
@@ -95,11 +92,7 @@ func (s *ipSliceValue) Append(val string) error {
 func (s *ipSliceValue) Replace(val []string) error {
 	out := make([]net.IP, len(val))
 	for i, d := range val {
-		var err error
-		out[i], err = s.fromString(d)
-		if err != nil {
-			return err
-		}
+		out[i] = s.fromString(d)
 	}
 	*s.value = out
 	return nil
diff --git a/ip_test.go b/ip_test.go
index 331d1d56..d5e4b853 100644
--- a/ip_test.go
+++ b/ip_test.go
@@ -27,7 +27,7 @@ func TestIP(t *testing.T) {
 		{"1.2.3.4", true, "1.2.3.4"},
 		{"127.0.0.1", true, "127.0.0.1"},
 		{"255.255.255.255", true, "255.255.255.255"},
-		{"", false, ""},
+		{"", true, "0.0.0.0"},
 		{"0", false, ""},
 		{"localhost", false, ""},
 		{"0.0.0", false, ""},
diff --git a/printusage_test.go b/printusage_test.go
index 203c6402..2cf7affd 100644
--- a/printusage_test.go
+++ b/printusage_test.go
@@ -4,8 +4,8 @@
 package pflag
 
 import (
-	"bytes"
 	"io"
+	"strings"
 	"testing"
 )
 
@@ -28,7 +28,7 @@ func setUpPFlagSet(buf io.Writer) *FlagSet {
 }
 
 func TestPrintUsage(t *testing.T) {
-	buf := bytes.Buffer{}
+	var buf strings.Builder
 	f := setUpPFlagSet(&buf)
 	f.PrintDefaults()
 	res := buf.String()
@@ -68,7 +68,7 @@ const expectedOutput2 = `      --long-form                    Some description
 `
 
 func TestPrintUsage_2(t *testing.T) {
-	buf := bytes.Buffer{}
+	var buf strings.Builder
 	f := setUpPFlagSet2(&buf)
 	res := f.FlagUsagesWrapped(80)
 	if res != expectedOutput2 {
diff --git a/string_slice.go b/string_slice.go
index 759ea4fb..3154b97b 100644
--- a/string_slice.go
+++ b/string_slice.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"encoding/csv"
 	"strings"
 )
@@ -32,7 +31,7 @@ func readAsCSV(val string) ([]string, error) {
 }
 
 func writeAsCSV(vals []string) (string, error) {
-	b := &bytes.Buffer{}
+	b := new(strings.Builder)
 	w := csv.NewWriter(b)
 	err := w.Write(vals)
 	if err != nil {
diff --git a/string_to_int.go b/string_to_int.go
index a672df00..d4b595db 100644
--- a/string_to_int.go
+++ b/string_to_int.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"fmt"
 	"strconv"
 	"strings"
@@ -54,7 +53,7 @@ func (s *stringToIntValue) Type() string {
 }
 
 func (s *stringToIntValue) String() string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	i := 0
 	for k, v := range *s.value {
 		if i > 0 {
diff --git a/string_to_int64.go b/string_to_int64.go
index bb6d043c..e0a1e211 100644
--- a/string_to_int64.go
+++ b/string_to_int64.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"fmt"
 	"strconv"
 	"strings"
@@ -54,7 +53,7 @@ func (s *stringToInt64Value) Type() string {
 }
 
 func (s *stringToInt64Value) String() string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	i := 0
 	for k, v := range *s.value {
 		if i > 0 {
diff --git a/string_to_int64_test.go b/string_to_int64_test.go
index 970de225..34123b62 100644
--- a/string_to_int64_test.go
+++ b/string_to_int64_test.go
@@ -4,9 +4,9 @@
 package pflag
 
 import (
-	"bytes"
 	"fmt"
 	"strconv"
+	"strings"
 	"testing"
 )
 
@@ -23,7 +23,7 @@ func setUpS2I64FlagSetWithDefault(s2ip *map[string]int64) *FlagSet {
 }
 
 func createS2I64Flag(vals map[string]int64) string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	i := 0
 	for k, v := range vals {
 		if i > 0 {
diff --git a/string_to_int_test.go b/string_to_int_test.go
index 9fda4376..838415c3 100644
--- a/string_to_int_test.go
+++ b/string_to_int_test.go
@@ -4,9 +4,9 @@
 package pflag
 
 import (
-	"bytes"
 	"fmt"
 	"strconv"
+	"strings"
 	"testing"
 )
 
@@ -23,7 +23,7 @@ func setUpS2IFlagSetWithDefault(s2ip *map[string]int) *FlagSet {
 }
 
 func createS2IFlag(vals map[string]int) string {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	i := 0
 	for k, v := range vals {
 		if i > 0 {
diff --git a/string_to_string.go b/string_to_string.go
index bda81ae3..b3dae9f1 100644
--- a/string_to_string.go
+++ b/string_to_string.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"encoding/csv"
 	"fmt"
 	"strings"
@@ -70,7 +69,7 @@ func (s *stringToStringValue) String() string {
 		records = append(records, k+"="+v)
 	}
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	w := csv.NewWriter(&buf)
 	if err := w.Write(records); err != nil {
 		panic(err)
diff --git a/string_to_string_test.go b/string_to_string_test.go
index b192c1fe..633ccb16 100644
--- a/string_to_string_test.go
+++ b/string_to_string_test.go
@@ -4,7 +4,6 @@
 package pflag
 
 import (
-	"bytes"
 	"encoding/csv"
 	"fmt"
 	"strings"
@@ -29,7 +28,7 @@ func createS2SFlag(vals map[string]string) string {
 		records = append(records, k+"="+v)
 	}
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	w := csv.NewWriter(&buf)
 	if err := w.Write(records); err != nil {
 		panic(err)
diff --git a/uint64.go b/uint64.go
index c930fb7f..8e4d8c52 100644
--- a/uint64.go
+++ b/uint64.go
@@ -30,7 +30,7 @@ func uint64Conv(sval string) (interface{}, error) {
 	if err != nil {
 		return 0, err
 	}
-	return uint64(v), nil
+	return v, nil
 }
 
 // GetUint64 return the uint64 value of a flag with the given name